The Russian Army has brought large numbers of troops and hundreds of pieces of military hardware to an area near the Ukrainian border, a Reuters correspondent reports.

The reporter said the heavy weapons included mobile rocket launchers, tanks, and artillery were brought from May 23-26 to the Kuminsky firing range, about 50 kilometers from part of Ukraine's Luhansk region that is controlled by pro-Russian separatists.

The Russian Defense Ministry said it had no immediate comment about the reported military build-up.

Kremlin spokesman Dmitry Peskov told Reuters during a conference call with reporters on May 27 that it was "inappropriate" to ask if the unmarked weaponry and troops in Russia near the Ukrainian border indicated an invasion was being prepared.

Moscow has repeatedly denied charges by Kyiv, NATO, and Western countries that it has sent troops or weapons to Ukraine, where fighting in the past year has killed at least 6,100 people.

NATO military commander General Philip Breedlove said earlier this month that he believes the rebels are preparing for a new offensive in eastern Ukraine.